Diols formed by ring-opening of epoxies

ABSTRACT

A polyol monomer comprising the formula: 
                         
R 1  and R 3  are —H, aliphatic, aromatic, or ether; R 2  is aliphatic, aromatic, ester, ether, or acrylic, and R 1  contains a hydroxyl group, R 3  contains a hydroxyl group, R 2  contains —O—CH 2 —CH(OH)—, or any combination thereof. The polyol monomer may be made by reacting an epoxy and an amine. Either the epoxy contains more than one epoxide groups, the amine contains a hydroxyl group, or both. A thermoset made by reacting the polyol monomer with a polyisocyanate.

This nonprovisional patent application is a divisional application ofU.S. patent application Ser. No. 10/346,061 filed on Jan. 17, 2003,incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to the formation of diols and polyolsand formation of polyurethanes therefrom.

2. Description of the Prior Art

Epoxy compounds have been reacted with amines to form thermosets.However, there have not been reports of the formation of low molecularweight products of epoxies and amines, suitable for solvent-freereaction with an isocyanate.

Polyurethanes have been made from alcohols and isocyanates. Thesereactions may cure quickly, even at low temperatures. The polymers aregenerally flexible, tough, and have good adhesion, but have inferiorchemical resistance in comparison to epoxy resins. Polyurethanes cansuffer from cathodic disbondment, in general due to the nature of thediols, which are susceptible to hydrolysis under alkaline conditions.Polyether diols are also used, but suffer from high water pick-up. Thetraditional focus for polyurethanes has been for the decorative andautomotive markets.

It is known that a polymer containing multiple hydroxyl groups can becross-linked with isocyanates. However, the starting polymer may be asolid or have a high viscosity. The polymer may need to be dissolved ina solvent in order to perform the cross-linking. The solvent must thenbe removed from the system, typically by evaporation.

It is also known that polymers with terminal hydroxyl groups, such aspoly(ethylene glycol), may also be cross-linked with an isocyanate.These polymers may also be a solid or have a high viscosity, requiringthe use of a solvent.

It is also known that a low molecular weight polyol, such as lowmolecular weight poly(ethylene glycol) can be cross-linked with anisocyanate. These polyols suffer from the drawback that they are notcompatible or soluble in the isocyanate.

Low molecular weigh esters and acrylics have been reacted withisocyanates to form thermosets. However, these polymers suffer fromhydrolysis under alkaline conditions.

There is need for a polyol monomer that is compatible with isocyanates,such it can cross-link with a polyisocyanate without the need forsolvent. The desirable system would have the chemical resistance of apolyepoxide and the curing and mechanical properties of a polyurethane.

SUMMARY OF THE INVENTION

The invention comprises a polyol monomer comprising the formula:

R² is selected from the group consisting of aliphatic, aromatic, ester,ether, or acrylic group; and R¹ and R³ are independently selected fromthe group consisting of —H, aliphatic, aromatic, and ether. R¹ containsa hydroxyl group, R³ contains a hydroxyl group, R² contains—O—CH₂—CH(OH)—, or any combination thereof.

The invention further comprises a thermoset formed by reacting apolyisocyanate with the above polyol monomer.

The invention further comprises a process of making a thermosetcomprising the steps of: providing an epoxy and an amine; wherein eitherthe epoxy contains more than one epoxide groups; the amine is selectedfrom the group consisting of primary amines, primary amino alcohols,secondary amino alcohols, and polyamines; or both; reacting the epoxywith the amine to make a polyol monomer; and reacting the polyol monomerwith a polyisocyanate.

The invention further comprises a process of making a thermosetcomprising the steps of: providing the above polyol monomer and reactingthe polyol monomer with a polyisocyanate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The polyol monomer can be made by reacting certain classes of amineswith certain classes of epoxy compounds. Instead of the usualpolymerization of these materials, a smaller molecule is formed. Theremay be no chain growth beyond a central epoxy or amine reacting in oneor more epoxide ring-opening reactions. The resulting polyol monomerwill have at least one secondary hydroxyl group and one or more primaryand/or secondary hydroxyl groups. The monomer must have at least twohydroxyl groups in order to form a thermoset with a polyisocyanate. Thismay be achieved by using a primary amines, a primary amino alcohol, asecondary amino alcohol, a polyamine, or a polyepoxy. The polyol monomermay be nonsaponifiable.

In one embodiment, shown in formula (1), a secondary amino alcohol isreacted with a monoepoxy in a ring opening reaction. Throughout thespecification and claims, the prefix poly-, as in polyol andpolyfunctional, means two or more of the specified functional group.This results in a polyol monomer having at a secondary hydroxyl groupfrom the reacting epoxide group and the primary or secondary hydroxylgroups from the amine. Although the alcohol group can also react with anepoxy, the amine reaction is very highly favored. An alcoholring-opening reaction can be ignored.

Examples of this embodiment include, but are not limited to, theproducts of the reaction of diethanolamine ormethyl(2-hydoxypropyl)amine with butyl glycidyl ether.

In another embodiment, shown in formula (2), a primary amino alcohol isreacted with a monoepoxy. A primary amine can react with two epoxies.This results in a polyol monomer having a secondary hydroxyl group fromeach epoxy and another hydroxyl group, either primary or secondary, fromthe alcohol. This embodiment can be varied by using less than two molesof epoxy per mole of primary amino alcohol to leave some amino hydrogensin the product.

Examples of this embodiment include, but are not limited to, the productof the reaction of ethanolamine with phenyl glycidyl ether.

In another embodiment, a secondary amino alcohol is reacted with apolyepoxy. Sufficient amine may be used to react with all epoxies. Thiswill also help avoid any reaction of hydroxyl groups with epoxide group.The resulting polyol monomer has at least two secondary hydroxyl groupsfrom the polyepoxy, and primary or secondary hydroxyl groups from theamine as shown in formula (3). This embodiment can be varied by using asecondary amine instead of a secondary amino alcohol, which would resultin no primary hydroxyl groups

Examples of this embodiment include, but are not limited to, the productof the reaction of methylethanolamine with triglycidyl ether ofglycerol.

In another embodiment, a primary amine is reacted with a monoepoxy.Since a primary amine can react with two epoxies, there can be at leasta 2:1 ratio of epoxy to amine. Otherwise, the product may not have twohydroxyl groups. This embodiment is shown in formula (4).

Examples of this embodiment include, but are not limited to, the productof the reaction of benzylamine with butyl glycidyl ether.

In another embodiment, a polyamine is reacted with a monoepoxy. Thepolyamine may include primary and/or secondary amines. This may produceonly secondary amines. This embodiment is shown in formula (5). Theratio of epoxy to amine may depend on the number of available aminohydrogens. The R′ and R′″ groups may be aliphatic, substitutedaliphatic, aromatic, substituted aromatic, and amine. The substituentsmay include hydroxyl groups, providing additional functionality for thesubsequent reaction with a polyisocyanate. The nitrogens, R′, and R′″may form a cyclic polyamine as in piperazine.

Examples of this embodiment include, but are not limited to, the productof the reaction of diethylenetriamine with butyl glycidyl ether.

All these embodiments are encompassed by the general structure:

R¹ and R³ can be —H, aliphatic, aromatic, or ether, and R² can bealiphatic, aromatic, ester, ether, or acrylic. The monomer has at leasttwo hydroxyl groups: the one shown in the general structure, and atleast one in R¹, R², or R³. R¹ and/or R³contain a hydroxyl group whenthe amine is an amino alcohol(formulas (1), (2), and (3)), when theamine is a primary amine (formulas (2) and (4)), and when the amine is apolyamine (formula (5)). When the epoxy is a polyepoxy, R² contains—O—CH₂—CH(OH)— (formula (3)). Such an R² group contains a hydroxylgroup. It may also be the case that combinations of R¹ and R³ withR²contain hydroxyl groups (formula (3)).

The polyol monomer may have a viscosity suitable for reacting with anisocyanate under ambient conditions in the absence of a solvent. Whenthe viscosity is too high, it may not be possible to achieve adequatemixing with the polyisocyanate to form a thermoset. It may also bepossible to reduce the viscosity of the polyol monomer to a suitableviscosity by reacting it with the polyisocyanate at an elevatedtemperature. Suitable polyol monomers may have molecular weights in therange of about 200 to about 3000.

Reactions between a secondary amine that is not an alcohol and amonoepoxy do not ordinarily produce a polyol monomer. The result has asingle secondary hydroxyl group. Such a compound can be used as anadditive as described below. An exception would be a diepoxy, where oneepoxide group had previously reacted with an alcohol or amine, making amonoepoxy having a hydroxyl group. Such a monoepoxy could be reacted asecondary amine to produce a polyol monomer. The product would be thatof formula (3). Another exception would be a primary amine, where oneamino hydrogen had previously reacted with an epoxy. The other aminohydrogen could then react with another epoxy. The product would be thatof formula (2) or (4).

The R¹R³N— group can be described as a residue of an amine, meaning thatthis moiety originated in an amine that reacted with an epoxy. Suitableamines include, but are not limited to, diethanol amine, ethanolamine,butyl amine, 2-amino-methyl-1-propanol, N-methyl-(2-propanol)amine,2-butyl-aminoethanol, N-methylethanolamine, 2-methyl isopropanol amine,2,2-ethoxy ethanol amine, methyl ethanol amine, benzyl ethanolamine,tert-butyl amine, diethyl amine, dipropyl amine, aniline, benzylamine,4-hydroxybenzylamine, cyclohexane diamine, ethylene diamine, diethylenetriamine, isophorone diamine, N-β-hydroxyethyl ethylene diamine,m-xylylene diamine, dibutyl amine, a polyamine, a substituted polyamine,and a cyclic amine.

The R²—CH₂—CH(OH) —CH₂— group can be described as a residue of an epoxy,meaning that this moiety originated in an epoxy that reacted with analcohol. Suitable epoxies include, but are not limited to, a glycidylether, butyl glycidyl ether, phenyl glycidyl ether, p-tertiary butylphenyl glycidyl ether, C₈-C₁₄ alkyl glycidyl ether, cresyl glycidylether, 2-ethylhexyl glycidyl ether, p-cumenol glycidyl ether, glycidylester of neodecanoic acid, diglycidyl ether of cyclohexane, diglycidylether of resorcinol, diglycidyl ether of bisphenol A, diglycidyl etherof bisphenol F, diglycidyl ether of 2-methyl resorcinol, diglycidylether of 1,4-butanediol, diglycidyl ether of neopentyl glycol,diglycidyl ether of 2,2-di(1,4-cyclohexyl)propane, and triglycidyl etherof glycerol.

It is to be understood that polyol monomers made from combinations ofmore than one amine and/or epoxies are within the scope of the claimedinvention. Similarly, the inclusion of an alcohol, in the mannerdisclosed in the U.S. Patent application No.10/346,099, filed on Jan.07, 2003, incorporated by reference, is also Within the scope of theclaimed invention. This is also the case for thermosets made from thesepolyol monomers and methods of making the same.

The R² can be such that it contains no more than one —O—CH₂—CH(OH)—group in the same linear chain as R¹R³N—. This polyol monomer would notinclude a polymerized epoxy. The polyol monomer may also be soluble inan isocyanate. Generally, a lower molecular weight polyol may be lesscompatible with isocyanates because they contain a higher percentage ofpolar hydroxyl groups.

The reaction of the amine and the epoxy can be performed by any meansknown in the art. The reaction may occur very quickly such that nocatalyst or solvent is required.

The reaction may be controlled through steric hindrance by choosing thestarting materials to form a secondary or tertiary structure. The molarratio of the amine and epoxy may be chosen to result in a desired degreeof reaction and quantity of hydroxyl groups. The polyol monomer may beless compatible with aliphatic isocyanates than with other isocyanates.

A thermoset can be formed by reacting the polyol monomer with apolyisocyanate according to formula (6).

R—OH represents the polyol monomer as described above. The hydroxylgroup can be from the original amine, or can be generated from thereaction of amine and epoxy. The formula shows only a single cross-link.The R group has at least one other hydroxyl group and the R⁴ group hasat least one other isocyanate group so that a thermoset is formed. Anexample possible structure of the thermoset is shown below. The polyolmonomer was made from butyl glycidyl ether and diethanolamine. Such apolyol monomer can then be reacted with diphenylmethane diisocyanate.

When the polyol monomer is soluble in the polyisocyanate, the reactioncan be solvent free. This results in no release of volatile organiccompounds. The reaction can be performed by any means known in the art.The reaction can be catalyzed by any catalyst known in the art tocatalyze this reaction including, but not limited to, organometalliccatalysts including those based on Sn, K, Ti, and Zn and tertiary aminecatalysts.

There are three commonly available types of isocyanates. Aromaticsinclude toluene diisocyanate and diphenyl methane diisocyanate.Aliphatics include hexamethylene diisocyanate dimers and trimers,4,4′-dicyclohexylmethane-diisocyanate, and isophorone diisocyanate.Others include tetramethylxylene diisocyanate. Other suitablepolyisocyanates include, but are not limited to, hexamethylenediisocyanate, diphenylmethane diisocyanate, cycloaliphaticpolyisocyanates, aliphatic polyisocyanates, an isocyanurate, biuret oftoluene diisocyanate, and biuret of hexamethylene diisocyanate.

These monomeric isocyanates may have some hazards in their highreactivity and health risks. These problems may be improved by the usedof polymeric isocyanates such as isocyanurate, adduct of TDI andglycerin, biuret of TDI, and biuret of HDI. As used herein, the term“polyisocyanate” includes both monomeric isocyanates and polymericisocyanates that contain more than one isocyanate functional group. Asused herein, the term “polyisocyanate ” includes both monomericisocyanates and polymeric isocyanates that contain more than oneisocyanate functional group, and the mention of any polyisocyanateincludes both monomeric and polymeric forms.

A variety of polyisocyanates are commercially available from Bayerincluding Desmodur N aliphatic isocyanates based on hexamethylenediisocyanate (N3200, N3300, and N3600), Desmodur Wbis(4-isocyanatocyclohexyl) methane, and Mondur CD, MRS, and E based ondiphenylmethane diisocyanate.

Generally, primary hydroxyl groups are more reactive with thepolyisocyanate than secondary hydroxyl groups. The amine, epoxy, andpolyisocyanate can be chosen to produce a thermoset with desiredproperties including degree of cross-linking, mechanical properties,adhesion, and chemical resistance.

The polyol monomer and the polyisocyanate may be mixed in astoichiometric ratio. The polyol monomer and the polyisocyanate may bestored separately and mixed together when needed to make the thermoset.The mixture can be applied as a coating, as the mixture may have a lowviscosity suitable for forming coatings. The mixture can then cure toform the thermoset. Curing times may be from a few seconds to the orderof minutes and may be done at any temperatures including, but notlimited to, about 10° C. or below. The reaction may proceed morefavorably when there is no contamination by water. Water may causeporosity or foaming.

The polyol monomer and the polyisocyanate can be mixed together as theyare sprayed onto a surface to be coated with the thermoset. This methodallow for little to no reaction until the mixture has been applied tothe surface. The spraying may be done with plural component sprayequipment, which may include a static mixer and/or an impingement mixer.

It may be desirable to react the polyol monomer and polyisocyanate withan alcohol additive so that the viscosity of the reaction mixture islower. The additive has a lower viscosity than that of the polyolmonomer. The additive may be a monofunctional alcohol or a polyol. Amonofunctional alcohol may be made by reacting a secondary amine that isnot an alcohol with a monoepoxy, as shown in formula (7). The productsof formulas (1) through (5) may also be used. R¹, R^(2,) and R³ may bethe same or different from those in the polyol monomer. However, usingthe same R¹, R², and R³ may not have a lower viscosity than the polyolmonomer.

An advantage of using this monofunctional alcohol additive is that ismay be chemically similar to the polyol monomer. The lower viscosity ofthe additive can help to reduce the viscosity of the reaction mixture,as would a solvent. However, unlike a solvent, the additive reacts withthe polyol monomer and polyisocyanate and is consumed in the reaction.Since the incorporated additive is chemically similar to the polyolmonomer, the properties of the thermoset are not substantially affectedby the presence of the additive.

The additive may also be made by the method disclosed in the previouslyreferenced U.S. patent application No.10/364,099. Other low molecularweight alcohols may also be used. The choice may depend on the desiredamount of viscosity reduction.

The thermoset may have desirable toughness, abrasion resistance,flexibility, and adhesion strength as is generally found inpolyurethanes. The thermoset may also have the chemical resistance,including hydrolytic stability and cathodic protection, of an epoxyresin. It may be resistant to caustic soda, methanol, and hydrocarbonfuel. The properties can be adjusted to form materials from tough, hardfilms to soft, pliable materials, fitting a wide range of applications.The properties are highly dependant on the starting materials used. Theproperties may be designed into the thermoset by choosing the isocyanateor combination of isocyanates, degree of polymeric isocyanate formation,and choice of polyol monomer.

The thermoset may be useful as a coating, which can be made as describedabove. Suitable substrates for the coating include, but are not limitedto, steel, metal, and concrete. A tank lining is one application of sucha coating. Such a lining may have good adhesion and chemical resistance.It may not be necessary to use a primer or topcoat.

The thermoset may also be useful as a repair compound. Higher viscositymaterials than are used for coatings may be appropriate, as the compoundmay fill a three-dimensional void.

A composite may also be made using the thermoset by reacting the polyolmonomer and the polyisocyanate in the presence of a fiber material, suchas glass fibers or carbon fibers. The fibers may impart additionalmechanical strength to the composite.

Having described the invention, the following examples are given toillustrate specific applications of the invention. These specificexamples are not intended to limit the scope of the invention describedin this application.

EXAMPLE 1

General procedure for forming the polyol monomer—Charge a 500 mLthree-neck vacuum flask with the appropriate stoichiometric ratio of theepoxy and the amine. Use approximately 0.1% excess or less epoxy toassure complete reaction (i.e. consumption) of the amine. The epoxy isadded in 10% portions over a period of one hour. Begin stirring themixture with moderate heating while noting the temperature of themixture. When the mixture turns clear, begin watching for signs of anexotherm. The mixture will initiate or display signs of an exotherm ator around 60° C. At this point the reaction vessel is placed in anambient temperature water bath and allowed to react until the producthas reached its maximum temperature. In general the mixture will peak at120° C. but can be higher if not placed into water bath at or around 60°C. An excessive exotherm greater than 150-160° C. should be avoided asit can result in etherification of secondary alcohols. Following theexotherm, the reaction product is then gently heated to 120° C. over aperiod of about one hour. The reaction product is vacuum distilled toremove all unreacted materials, water, and volatiles beginning at 120°C. and allowed to cool to approximately 90° C. Vacuum distillationcontinues until no further violent boiling is observed. This signifiesthat all moisture and unreacted glycidyl ether has been removed. Usuallyno more than one to three percent of volatiles are removed this way. Theresulting product is cooled and placed in a suitable storage containerfor future use.

EXAMPLE 2

Reaction of monoepoxies with primary amines—In these reactions, twomoles of a monoepoxy are reacted with one mole of a primary amineaccording to the procedure of Example 1. This molar ratio is usedregardless of whether the amine is an amino alcohol. Combinations thatwere reacted included butyl glycidyl ether with benzyl amine, o-toluenylglycidyl ether with butyl amine, phenyl glycidyl ether withethanolamine, and butyl glycidyl ether with p-hydroxybenzylamine.

EXAMPLE 3

Reaction of monoepoxies with secondary amino alcohols—In thesereactions, two moles of a monoepoxy are reacted with one mole of asecondary amino alcohol according to the procedure of Example 1.Combinations that were reacted included butyl glycidyl ether withdiethanolamine and p-cumenol glycidyl ether with methylethanolamine.

EXAMPLE 4

Reaction of polyepoxies with secondary amino alcohols—In thesereactions, one mole of a polyepoxy is reacted with two or more moles ofa secondary amino alcohol according to the procedure of Example 1. Onemole of secondary amino alcohol is used for each epoxide group in thepolyepoxy. Combinations that were reacted included 1 mole diglycidylether of bisphenol F with 2 mole diethanolamine and 1 mole triglycidylether of glycerin with 3 mole methylethanolamine.

EXAMPLE 5

Reaction of monoepoxies with polyamines—In these reactions, one mole ofa polyamine is reacted with two or more moles of a monoepoxy accordingto the procedure of Example 1. Up to one more of monoepoxy is used foreach amino hydrogen in the polyamine. Combinations that were reactedincluded 5 moles butyl glycidyl ether with 1 mole diethylene triamine.

EXAMPLE 6

Reaction of monoepoxies with secondary amines to form an alcoholadditive—In these reactions, one mole of a monoepoxy is reacted with onemole of a secondary amine according to the procedure of Example 1. Thisformed alcohol additives containing a single hydroxyl group.Combinations that were reacted included butyl glycidyl ether withdibutyl amine and phenyl glycidyl ether with dipropyl amine.

EXAMPLE 7

General procedure for forming the thermosets—The thermoset was made bymixing together a polyol monomer and a polyisocyanate. The mixturesolidified without the use of a catalyst or heating. The thermoset wasformed as a shaped article, such as a disk.

EXAMPLE 8

Formation of thermosets from ethanolamine—Polyol monomers made from thereaction of ethanolamine and a variety of monoepoxies including butylglycidyl ether and phenyl glycidyl ether were reacted with a variety ofpolyisocyanates including triisocyanurates, hexamethylene diisocyanates,diphenylmethylene diisocyanates, and bis(4-isocyanatocyclohexyl)methane. All formed tough thermosets.

EXAMPLE 9

Formation of thermosets from diethanolamine—Polyol monomers made fromthe reaction of diethanolamine and a variety of monoepoxies includingbutyl glycidyl ether and phenyl glycidyl ether were reacted with avariety of polyisocyanates including triisocyanurates, hexamethylenediisocyanates, diphenylmethylene diisocyanates, andbis(4-isocyanatocyclohexyl) methane. All formed tough thermosets. Thesame was done with bifunctional epoxies.

EXAMPLE 10

Formation of thermosets from methylethanolamine—Polyol monomers madefrom the reaction of methylethanolamine and a variety of monoepoxiesincluding butyl glycidyl ether and phenyl glycidyl ether were reactedwith a variety of polyisocyanates including triisocyanurates,hexamethylene diisocyanates, diphenylmethylene diisocyanates, andbis(4-isocyanatocyclohexyl) methane. All formed tough thermosets. Thesame was done with bifunctional epoxies.

EXAMPLE 11

Formation of thermosets from polyamines—Polyol monomers made from thereaction of butyl glycidyl ether with polyamines including diethylenetriamine, ethylene diamine, 1,2-cyclohexane diamine, xylylene diamine,isophorone diamine, and N-β-hydroxyethyl ethylene diamine were reactedwith a variety of polyisocyanates including triisocyanurates,hexamethylene diisocyanates, diphenylmethylene diisocyanates, andbis(4-isocyanatocyclohexyl) methane. All formed tough thermosets.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is therefore to beunderstood that, within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described.

1. A polyol monomer comprising the formula:

wherein R¹ is a divalent radical selected from the group consisting ofaliphatic, aromatic, and ether-containing group; wherein R² is free—O—CH₂—CH(OH)— groups; wherein R²—O—CH₂—CH(OH)—CH₂— is a residue of anepoxy selected from the group consisting of butyl glycidyl ether, phenylglycidyl ether, p-tertiary butyl phenyl glycidyl ether, C₈-C₁₄ alkylglycidyl ether, cresyl glycidyl ether, 2-ethylhexyl glycidyl ether, andp-cumenol glycidyl ether; and wherein the polyol monomer is free ofepoxy groups and amino hydrogens.
 2. The polyol monomer of claim 1,wherein the polyol monomer is soluble in an isocyanate.
 3. The polyolmonomer of claim 1, wherein the polyol monomer has a viscosity suitablefor reacting with an isocyanate under ambient conditions in the absenceof a solvent.
 4. The polyol monomer of claim 1, wherein the polyolmonomer has a molecular weight no more than about
 3000. 5. The polyolmonomer of claim 1, wherein the polyol monomer has a molecular weight noless than about
 200. 6. The polyol monomer of claim 1, wherein N—R¹—N isa residue of a diamine selected from the group consisting of cyclohexanediamine, ethylene diamine, isophorone diamine, N-β-hydroxyethyl ethylenediamine, and m-xylylene diamine.
 7. The polyol monomer of claim 1,wherein the polyol monomer is